Last year UK consumers spent £475m on unforeseen car hire costs and a fifth admit they won’t rent one when abroad for fear they’ll be ripped off.

New research from price comparison site TravelSupermarket revealed that 51% are worried about hiring a car to drive abroad while 53% of those who had rented said they were overcharged.

Of those who were overcharged, the average amount paid on top of the agreed service is £116.15 and the most common car hire extra charges centre around a tank of fuel.

Some policies state you collect the car with a full tank and you need to return it empty. These customers have been stung with an average cost of £83.

In other cases, customers have been caught with charges of £98 for not returning the car with the agreed amount of fuel.

Some drivers have been stung with charges of £168 for excess mileage and others have had to fork out £80 for the vehicle to be cleaned.

At the pickup desk, some users report the ‘hard sell’ for a car upgrade and TravelSupermarket said if your car isn’t available, you should be given a better car free of charge or a smaller car where the different is refunded.

Bob Atkinson, TravelSupermarket’s travel expert, said: “Car hire is a wonderful way to really get the most out of your holiday. The right planning will not only help you get a good deal on your car hire package but will prevent you being charged for either unexpected or overpriced items at the rental station.”

Top tips to avoid car hire rip offs

While car hire firms have been told to make all fees and optional extras clearer, here are some tips to avoid being ripped off on your hols:

• Never rent in resort, pre-book – booking a vehicle online in advance will not only save you money but will also mean there’s a wider pool of cars to choose from. If you leave it until you arrive at your destination, you’re likely to be left out of pocket and with a car that isn’t suited to your needs.

• Beware the ‘full – empty’ fuel policy – a big issue for one in 10 car hirers is the “full – empty policy”, where you pay upfront for a tank of petrol and can return it empty. While this may seem like an attractive offer, look for car hire firms that allow you to return it with the same amount of fuel you had when you picked it up – this means you won’t be charged an inflated price for the petrol and you won’t pay for fuel you haven’t used.

• Paying for extras you could have brought yourself – 12% of those surveyed admit they’ve been charged for car hire extras which they could have brought themselves had they known it would incur a fee. Be sure to read the fine print before booking to make sure you’re aware of all you need to bring. Things like sat navs can be expensive to hire, but many of us own them already, so this is an easy cost to save on.

• Accidents in a hire car – almost half of those who have hired a car are hesitant about hiring a car abroad owing to fear that having an accident or causing minor damage would cost them more than in their own car. When you hire a car, insurance is included but it often comes with incredibly high excess charges (up to £2,000). If you buy an excess waiver policy online in advance of your holiday, you can pay just £3 a day (compared with up to £20 if you don’t plan ahead) and it can save you thousands, should you have an accident.

• Your hire car is suddenly ‘unavailable’ – 18% of hirers have experienced a hard sell for an upgrade at the pickup desk, and often this is blamed on the fact that the car in the category you booked is no longer available. Unsurprisingly, they will offer you an upgrade for a price. But, don’t fall for it. You should either be offered a higher category car for no extra cost or a lesser one with the appropriate refund. Stand your ground on this.

• Overcharging you by asking for payment in sterling – Another trap to watch out for is not being given the option to pay in the local currency when you collect your vehicle – even though firms are legally required to give customers a choice. Paying in sterling can result in you being charged over the odds as firms may use an uncompetitive exchange rate. Before entering your pin number, have a look at the amount – and check the currency being used.